1. Field of the Invention
This invention relates to a magnetic disk unit used as an external storage of computers and a support member for magnetic disk substrate used for this.
2. Description of the Prior Art
Hitherto, as shown in FIG. 5, the magnetic disk unit is fixed by inserting multiple pieces of magnetic disk substrate 12 and spacer 20 alternately into a hub 11 fixed to a rotary shaft 10, and lastly pressing with a shim 30 and a clamp 40 and tightening with a screw 13. And by allowing the magnetic head 14 to move on the surface of the magnetic disk substrate 12 free from contact while the magnetic disk substrate 12 is being rotated by rotation of the above rotary shaft 10, the information is designed to be written to or read from the specified position of the magnetic disk substrate 12.
In recent years, these magnetic disk units 50 are required to achieve an extremely small levitation rate for the distance between the magnetic head 14 and the magnetic disk substrate 12 as the densification of information increases, and for this purpose, the magnetic disk substrate 12 was formed with ceramics or glass which is highly rigid and is difficult to generate deformation, and the support member such as spacers 20 for fixing the magnetic disk substrate 12, shims 30, and clamps 40 were formed with ceramics or glass same as those in the case of magnetic disk substrate 12 in order to prevent deformation of the magnetic disk 12 caused by a thermal expansion difference and to reduce weight (Japanese Patent Publication No. Hei 5-80745 and Japanese Paten Application Laid Open No. Sho 61-148667).
For example, the spacer 20 for holding the magnetic disk substrate 12 to given intervals is made of alumina ceramics as shown in FIG. 8 and formed into a ring shape 21.
On the other hand, in Japanese Patent Laid Open No. Sho 51-118408, support members such as spacers and shims are disclosed, which are designed to have a plurality of air grooves cut radially on the contact surface with the magnetic disk substrate 12 and form an air layer in the air groove in order to relieve stresses applied to the magnetic disk substrate 12 during clamping.
However, because ceramics or glass which comprises support members such as the spacer 20, shim 30, clamp 40, etc. are fragile, there was a fear of generating chipping at the edge due to the stress at the time of clamping. This broken piece may damage the magnetic disk substrate 12 or break the magnetic head 14, if it enters the clearance between the magnetic disk substrate 12 and the magnetic head 14 levitating on it.
On the other hand, with the support member designed to have air grooves cut on the contact surface and form air grooves in them, the greater the ratio of the air grooves accounting for the contact surface, the smaller is the contact surface with the magnetic disk substrate 12, possibly resulting in strain in the magnetic disk substrate 12. Consequently, it was unable to decrease the flatness of the magnetic disk substrate 12 at the time of clamping and it was unable to minimize the levitation rate of the magnetic head 14. In particular, when the magnetic disk substrate 12 deforms in the shape of a letter V, the magnetic head 14 collides against the magnetic disk substrate 12 to result in breakage.
In recent years, it has been known that static electricity is charged in the magnetic disk substrate 12 when the information is read or written and noise is generated to destroy the recording contents, but charging of the magnetic disk substrate 12 was unable to be prevented because ceramics and glass are, in general, insulating materials.
Under these circumstances, in this invention, the support members such as shims, clamps, and spacers are formed with ceramics or glass and at the same time the ratio of the actual contact surface is designed to be 50-95% as well as the flatness of this contact surface is made to be 3 .mu.m or less.
It is an object of this invention to provide a magnetic disk unit comprising one or a plurality of magnetic disk substrate arranged on a nearly cylindrical hub to be fixed to a rotating shaft via ring-form spacers and shims and held by clamps, the said magnetic disk substrate being made from ceramics or glass and held by spacers and shims whose actual contact area ratio with the magnetic disk substrate is designed to be 50-95%, wherein the flatness of the contact surface is designed to be 3 .mu.m or less.
It is another object of this invention to provide a magnetic disk unit in which a through hole perpendicular to the contact surface of support member such as shims or clamps is drilled to dispose springs in the through hole or to fill the through hole with conductive materials or cover the surface with conductive materials in order to achieve conductivity between the top and the bottom of the contact surfaces and prevent charging of the magnetic disk.
This invention relates to a support member for magnetic disk substrate for holding the magnetic disk substrate to a specified position and a magnetic disk unit comprising one or a plurality magnetic disk substrate held to a hub by means of this.
Hitherto, as shown in FIG. 12, the magnetic disk unit was fixed by alternately inserting a plurality of magnetic disk substrate 115 and spacer 111 into a hub 114 fixed to a rotary shaft 113 and lastly pressing them with shims 110 and clamps 112 and tightening with screws 116. And with the magnetic disk substrate 115 being rotated by the rotation of the rotary shaft 113, the magnetic head 117 was allowed to move on the surface of the magnetic disk substrate 115 free from contact so that the information is written or read at a specified position of the magnetic disk substrate 115.
In recent years, as the information density and the storage capacity increase, the magnetic disk unit 150 is required to further minimize the distance between the magnetic head 117 and the magnetic disk 115, increase flatness of the magnetic disk substrate 115, and improve smoothness of its surface, and, therefore, there is disclosed a magnetic disk substrate 115 using ceramics or glass, in which increased surface strength and improved surface smoothness are highly effectively achieved, and the support members such as spacers 111, shims 110, and clamps 112 for fixing and supporting the magnetic disk substrate 115 are formed with ceramics or glass for preventing deformation of the magnetic disk substrate 115 caused by thermal expansion difference as well as for reducing weight (Japanese Patent Publication No. Hei 5-80745, Japanese Non-examined Patent Publication No. Sho 61-148667).
However, because ceramics or glass composing the support member are, in general, insulating materials, it has recently been known that supporting the magnetic disk 115 with these support members charges the magnetic disk substrate 115, generates noises in writing or reading the information, and possibly destroys the recording contents, and therefore, there is disclosed a method for preventing charging of the magnetic disk 115 by using the support member with the contact surface with the magnetic disk substrate 115 coated with metallic film such as aluminum, zinc, etc. (Japanese Non-examined Patent Publication No. Hei 2-226566).
However, because the support member with the contact surface coated with metallic film causes a large thermal expansion difference between the ceramics or glass constituting the substrate and the metallic film, there is a problem in which the flatness of the contact surface is impaired by the heat resulting from high-speed rotation. In addition, there is a problem of burr specific to metal. Consequently, because forming a magnetic disk unit 150 using this support member causes strain in the magnetic disk substrate 115 and impairs the parallelism between magnetic disk substrates 115, it is unable to reduce the levitation rate of the magnetic head 117, possibly causing the magnetic head 117 to come in contact with the magnetic disk substrate 115 and breaking the magnetic head 117.
In addition, there is a fear of peeling of the metallic film due to the thermal expansion difference with the ceramics or glass forming the substrate, and as a result, there is a problem in which static electricity charged on the magnetic disk substrate 115 is unable to be released.
Furthermore, there is a problem in which when the inside and outside edges of the support member are sharp edges, the metallic film thickness coated to the edges become thinner, causing disconnection according to circumstances , and static electricity is unable to be released.
In addition, there is another problem in which since ceramics or glass forming the support member are fragile, sharp edges may cause chipping due to stress at the time of clamping and this broken piece entering the clearance between the magnetic disk substrate 115 and the magnetic head 117 levitating above the substrate may damage the magnetic disk substrate 115 or break the magnetic head 117.
Consequently, in the magnetic disk unit 150 in which the magnetic disk substrate 115 is held with these support members, it is difficult to achieve sufficiently high densification and high capacity of the information and static electricity charged in the magnetic disk substrate 115 may generate noise in reading or writing the information and may destroy the recording contents.
In view of the foregoing problems, it is a main object of this invention to provide a magnetic disk support members made of ceramics or glass, such as shims, clamps, and spacers, comprising the inside and outside edges of the support members provided with 0.004-0.5-mm-wide taper or curvature and at least the contact surface with the magnetic disk substrate and the inner circumferential surface coated with conductive ceramic film 0.1-3 .mu.m thick.
It is an object of this invention to provide a magnetic disk unit by holding one or a plurality of magnetic disk substrate comprising ceramics or glass to the hub fixed to a rotary shaft and comprising conductive material via a spacer and/or shim in a ring form made of ceramics or glass and with 0.04-0.5 mm taper or curvature provided on inner and outer edges and at least with the contact surface with the magnetic disk and the inner circumferential surfaces coated with 0.1-3 .mu.m conductive hard film.
More specifically, this invention is coated with any one type of conductive hard films of TiC, TiN, ZrN, HfC, TaC, ZrC, WC, VC, NbC, TiB.sub.2, ITO (Indium Tin Oxide), and DLC (Diamond-like Carbon).
This invention relates to magnetic disk substrate support members such as spacers, shims, and clamps for holding the magnetic disk substrate to a specified position and a magnetic disk unit comprising glass magnetic disk substrates held by these support members.
Hitherto, as illustrated in FIG. 17, the magnetic disk unit was fixed by alternately inserting a plurality of magnetic disk substrate 215 and spacer 211 into a hub 214 fixed to a rotary shaft 213 and lastly pressing them with shims 210 and clamps 212 and tightening with screws 216. And with the magnetic disk substrate 215 being rotated by the rotation of the rotary shaft 213, the magnetic head 217 was allowed to move on the surface of the magnetic disk substrate 215 free from contact so that the information is written or read at a specified position of the magnetic disk substrate 215.
In recent years, as the information density and the storage capacity increase, the magnetic disk unit 250 is required to further minimize the distance between the magnetic head 217 and the magnetic disk 215, increase flatness of the magnetic disk substrate 215, and improve smoothness of its surface, and, therefore, there is disclosed a magnetic disk substrate 215 using ceramics or glass, in which increased surface strength and improved surface smoothness are highly effectively achieved, and the support members such as spacers 211, shims 210, and clamps 212 for fixing and supporting the magnetic disk substrate 215 are formed with ceramics or glass for preventing deformation of the magnetic disk substrate 215 caused by thermal expansion difference as well as for reducing weight (Japanese Patent Publication No. Hei 5-80745, Japanese Non-examined Patent Publication No. Sho 61-148667).
However, because ceramics or glass composing the support member are, in general, insulating materials, it has recently been known that supporting the magnetic disk 215 with these support members charges the magnetic disk substrate 215, generates noises in writing or reading the information, and possibly destroys the recording contents, and therefore, there is disclosed a method for preventing charging of the magnetic disk 215 by using the support member with the contact surface with the magnetic disk substrate 215 coated with metallic film such as aluminum, zinc, etc. (Japanese Non-examined Patent Publication No. Hei 2-226566).
However, because the support member with the contact surface coated with metallic film causes a large thermal expansion difference between the ceramics or glass constituting the substrate and the metallic film, there is a problem in which the flatness of the contact surface is impaired by the heat resulting from high-speed rotation. In addition, there is a problem of burr specific to metal. Consequently, because forming a magnetic disk unit 250 using this support member causes strain in the magnetic disk substrate 215 and impairs the parallelism between magnetic disk substrates 215, it is unable to reduce the levitation rate of the magnetic head 217, possibly causing the magnetic head 217 to come in contact with the magnetic disk substrate 215 and breaking the magnetic head 217.
In addition, there is a fear of peeling of the metallic film due to the thermal expansion difference with the ceramics or glass forming the substrate, and as a result, there is a problem in which static electricity charged on the magnetic disk substrate 215 is unable to be released.
Furthermore, though the metallic film is coated in a thin film form to prevent damage to flatness of the contact surface, because a slight sliding occurs between the magnetic disk substrate 215 and the support member due to high-speed rotation, causing wear or peeling of the metallic film with small hardness, there is a problem that static electricity is unable to be released.
In addition, there is another problem in which there is about 2 to 5.times.10.sup.-6 /.degree.C. thermal expansion difference between the support member and the glass magnetic disk substrate even in the support member comprising conductive ceramics, generating strain in magnetic disk substrate 215 in a similar manner as in the case of the support member with the contact surface coated with metallic film or impairing the parallelism between magnetic disk substrates 215.
In the magnetic disk unit 250 required for further increased density and larger capacity, there has not been obtained any unit 250 which satisfies the requirements for those using the above support members.
In view of the foregoing problems, in this invention, the magnetic disk substrate support members such as shims, spacers, and clamps are formed with conductive forsterite ceramics whose volume specific resistance is less than 10.sup.7 .OMEGA..multidot.cm.
This invention constructs a magnetic disk unit by inserting and fixing successively the above-mentioned support members and glass magnetic disk substrate into a hub comprising conductive materials.
This invention relates to a magnetic disk unit used as an external storage for computers and magnetic disk substrate support members used for the unit.
The magnetic disk unit used hitherto is designed to mount a plurality of magnetic disk substrates 315 and spacers 311 alternately to the hub 314 fixed to the rotary shaft 313, as shown in FIG. 20, press shims 310 and clamps 312, and tighten screws 316 for fixing. Rotating these magnetic disk substrates 315 by the rotation of the rotary shaft 313, the magnetic head 317 moves on the surface of each magnetic disk substrate 315 without contact, and writes or reads the information at a specified position of each magnetic disk substrate 315.
For the material of the magnetic disk substrate 315, aluminum substrates or glass substrates are used, the surface of which magnetic film is formed. On the other hand, for the support materials such as shims 310, spacer 311, and clamps 312, metallic materials such as aluminum or stainless steel are used.
In these magnetic disk units, in order to increase the recording density, the distance between the levitated magnetic head 317 and the magnetic disk substrate 315 should be minimized, and presently, this distance is required to achieve a levitation rate as small as 0.1 .mu.m or less. Consequently, the present applicant has already proposed to use ceramic materials with high rigidity and small thermal expansion rate as a material for the magnetic disk substrate (for example, see Japanese Patent Publication No. Hei 3-64933, etc.). In addition to this, glass-coated ceramics, YAG, titanium, silicon, carbon, etc. have been proposed for the material of magnetic disk substrates 315.
However, with conventional metal shims 310 and spacers 311, and clamps 312, the maximum flatness achieved for the surface in contact with the magnetic disk substrate 315 is at most 3 .mu.m and at the same time because it is easy to deform when tightened due to low rigidity, bending is likely to occur in the magnetic disk substrate 315 at the time of tightening. Because when the magnetic disk substrate 315 bends, it is likely to collide against the magnetic head 317, the levitation rate of the magnetic head 317 is unable to be reduced, giving rise to inconvenience that higher density recording is not possible.
When ceramic magnetic disk substrate 315 is used, if support members such as shims 310, spacers 311, and clamps 312 are made of aluminum or other metals, strain is generated in the magnetic disk substrate 315 or tightening becomes loose when high temperature occurs due to high-speed rotation during application because the difference between thermal expansion ratios of both is large.
Therefore, in a preferred embodiment of this invention, the magnetic disk substrate support members such as shims, spacers, and clamps are formed with ceramics or glass with thermal expansion ratio lower than 12.times.10.sup.-6.degree.C., and at the same time the flatness of the surface in contact with magnetic disk substrate is designed to be 3 .mu.m or lower. And combining this support member and a plurality of magnetic disk substrates, a magnetic disk unit is composed.
The support members referred to in this invention include spacers used for holding a plurality of magnetic disk substrate to specified intervals, and shims and clamps for mounting this magnetic disk substrate to the rotary shaft.
This invention relates to the magnetic disk unit used for external storage of computers and the support member for magnetic disk substrate used for the unit.
The magnetic disk unit used hitherto is designed to mount a plurality of magnetic disk substrates 415 and spacers 411 alternately to the hub 414 fixed to the rotary shaft 413, as shown in FIG. 25, press shims 410 and clamps 412, and tighten screws 416 for fixing. Rotating these magnetic disk substrates 415 by the rotation of the rotary shaft 413, the magnetic head 417 moves on the surface of each magnetic disk substrate 415 without contact, and writes or reads the information at a specified position of each magnetic disk substrate 415.
For the material of the magnetic disk substrate 415, aluminum substrates or glass substrates are used, the surface of which magnetic film is formed. On the other hand, for the support materials such as shims 410, spacers 411, and clamps 412, metallic materials such as aluminum or stainless steel are used (see for example Japanese Patent Publication No. Sho 61-278023).
In these magnetic disk units, in order to increase the recording density, the distance between the levitated magnetic head 417 and the magnetic disk substrate 415 should be minimized, and presently, this distance is required to achieve a levitation rate as small as 0.1 .mu.m or less. Consequently, the present applicant has already proposed to use ceramic materials with high rigidity and small thermal expansion rate as a material for the magnetic disk substrate (for example, see Japanese Patent Publication No. Hei 3-64933, etc.). In addition to this, glass-coated ceramics, YAG, titanium, silicon, carbon, etc. have been proposed for the material of magnetic disk substrates 415.
However, with conventional metal shims 410 and spacers 411, and clamps 412, the maximum flatness achieved for the surface in contact with the magnetic disk substrate 415 is at most 5 .mu.m and at the same time because it is easy to deform when tightened due to low rigidity, bending is likely to occur in the magnetic disk substrate 415 at the time of tightening. Because when the magnetic disk substrate 415 bends, it is likely to collide against the magnetic head 417, the levitation rate of the magnetic head 417 is unable to be reduced, giving rise to inconvenience that higher density recording is not possible.
When ceramic magnetic disk substrate 415 is used, if support members such as shims 410, spacers 411, and clamps 412 are made of aluminum or other metals, strain is generated in the magnetic disk substrate 415 or tightening becomes loose when high temperature occurs due to high-speed rotation during application because the difference between thermal expansion ratios of both is large.
Therefore, a proposal has been made to form the support members such as shims, 410, spacers 411, clamps 412, etc. with ceramics, but in this case, hardness of the support member is excessively high and the magnetic film formed on the surface of the magnetic disk substrate 415 at the time of high-speed rotation is scraped away by ceramics, causing metallic powder.
In this invention, magnetic disk base support members such as shims, spacers, clamps are formed with ceramics with thermal expansion ratio 20.times.10.sup.-6.degree.C., and the surface in contact with the magnetic disk substrate is coated with film of 450 kg/mm.sup.2 or less, and the flatness of this contact surface is 5 .mu.m or less. And combining these support members and magnetic substrates, a magnetic disk unit is composed.
The support members referred to in this invention include spacers used for holding a plurality of magnetic disk substrate to specified intervals, and shims and clamps for mounting this magnetic disk substrate to the rotary shaft.
According to this invention, because support members are formed with ceramics, a large rigidity can be achieved and the flatness of the contact surface with the magnetic disk can be improved, it is possible to maintain the magnetic disk to a high accuracy. Because the film with small hardness is provided on the support member surface, scraping of magnetic film on the magnetic disk surface can be prevented.